This invention relates to sensors for use with internal combustion engines, transmissions, differentials and vehicular oil systems, and more particularly to oil level sensors for such engines and the like which are particularly suited for use with electronic and computerized control systems.
Various oil level sensors are currently being used in automotive and related applications to supply oil level information to engine control systems, including computerized control systems. Such information is particularly important in the case of heavy equipment such as mining and other heavy construction equipment. The working environment of the engine in these cases is particularly harsh and the equipment is expensive. Although the present invention is especially suited to such environments, it is not so limited. Some sensors which are currently being used to sense the oil level in internal combustion engines are known as thermal dissipation sensors. These sensors are relatively low in cost and are relatively easy to interface with control systems, but they do have certain features which could be improved. For example, the power consumption of thermal dissipation sensors is undesirably high while the durability of such sensors (an important quality considering the extremes which such sensors have to endure) is less than one would like. In addition, these sensors tend to cause the amount of carbon in the oil to increase, which is not a desirable feature
Float switches are also used for oil level sensing, and these switches are relatively low in cost. However, float switches are not particularly reliable and they suffer from a limited temperature range. Dipsticks and sightglasses have also been used as oil level sensors. These latter sensors are relatively inconvenient to use and they do not interface well with electronic or computerized control systems. Their utility is further reduced because of the fact that they must in general be read manually. A capacitive probe sensor is also available for sensing oil level. It has the advantage of being a low power consuming device, but it does suffer from a reduced operating margin. That is, present capacitive probes are not believed to be adequately sensitive to the minute capacitance changes occurring as oil levels change throughout the entire range of operating conditions of the engine itself.